While not necessarily limited thereto, the present invention is particularly adapted for use in the production of liquid crystal displays of the type shown in copending application Ser. No. 136,441, filed Apr. 22, 1971 and assigned to the Assignee of the present application, now U.S. Pat. No. 3,371,986, issued May 8, 1973. Optical display devices of the type shown in the aforesaid patent convert electrical intelligence into optical images with the use of a shutter device comprising a layer of liquid crystal material sandwiched between opposing parallel plates coated with transparent conducting films. These plates, with the liquid crystal material therebetween, are disposed between and parallel to a pair of polarizers such that when an electrical potential is established across the conducting films and the liquid crystal layer, the device will change from a light transmitting to opaque medium, or vice versa, depending upon the orientation of the two polarizers. By forming the two conducting films in the shape of a desired optical image, that image can be made to appear or disappear, depending upon whether a potential is established between the conducting films. Furthermore, by creating separate conducting areas, as by etching the conducting films, any number of conductive regions can be switched ON while other regions are not affected to produce any one of a number of different images with the same liquid crystal sandwich assembly.
In constructing a liquid crystal display of the type described above, it is necessary to unidirectionally rub the facing surfaces of the transparent parallel plates between which the layer of liquid crystal material is disposed. By orienting the directions of rubbing on the respective plates transverse to each other, a twisted nematic structure is achieved; and assuming that the directions of rubbing are at right angles to each other, the liquid crystal material will rotate the plane of polarization of polarized light by 90.degree.. When such a device with a 90.degree. twist is placed between parallel polarizers, no light will be transmitted at zero voltage and it will be the equivalent of two crossed polarizers. When an electric field is applied to the transparent conducting films on the respective plates, however, the structure will untwist at a well-defined voltage and allow light transmission. If, however, the same device is placed between crossed polarizers, then at zero voltage light is transmitted and the polarizers will effectively act as though they are parallel. However, with the application of a critical voltage, the plane of polarization will no longer be rotated 90.degree. and no light will be transmitted.